Dear Shamudra,

To start with, your question is very much generic. It is not very clear what kind of CFD solvers you are relating to: A commercial CFD solver like Fluent, an open source library like OpenFOAM or it is about a in-house CFD solver developed by you. However, in a generic sense, Grid/Time convergence and flow solver validation is the foundation of the accuracy of the simulation results. I will suggest you to first optimise your mesh and time step through convergence studies before going for validating others results. This might save some time for you.

If you are validating your own code, it is always advisable to match with experimental results (if available) and not with another CFD results in the first priority. The other option, it if you are using any well established open source solver or commercial solver, search for the validation studies already carried out in the literature and you can cite them for your reference.

Please refer to one of my recent publication in Physics of Fluids to get an idea about how the convergence and validation studies should be performed.

1. Chandan Bose, Sunetra Sarkar (2018) : Investigating chaotic wake dynamics past a flapping airfoil and the role of vortex interactions behind the chaotic transition, Physics of Fluids, Volume 30, Issue 4, 047101. DOI: 10.1063/1.5019442.

Best regards,

Chandan

I generally use commercial software ANSYS Fluent for CFD related problems

It depends on the type of the problem you solve.

In general, for an industry level problem, mesh generation (pre-processing) is the most time consuming part. However, for a research based problem, solver convergence and validation may be time-consuming.

Debugging your code is the most time consuming part if you are developing your CFD code from scratch. For me time for debigging= 4x time writing the code...:p. Some other part also take time for example grid convergence since you need to run a lot of simulations for the same case but for different resolution in order to get a converged value. For validation, try to validate your result with some good journal papers (ex-JFM, phy of fluid, comp. phy., AIAA, phys. review...etc.)

Grid (mesh) generation takes the longest and generating a high quality grid takes time. The second is mesh sensitivity study.

Validation is very important when it comes to using a particular CFD solver of your choice (trust). Validation section has to be included in a paper if you are looking forward to publish your research especially in a Q1 journal.

Interesting

In CFD:

Grid and Mesh Generation can take up a lot of time to get quality meshes.

Sometimes, you might have to remesh the whole geometry after you run your CFD code for some time, if you have complex phenomenon like moving meshes.

Yes, verification and validation is extremely important for CFD codes, perhaps the only. If you are using a commercial code, your CFD schemes are already verified,

but you must report validation studies for publication.

For example, how does your solution vary with the grid size, and if you are using models, then how does your solution vary with different models would be of prime interest. You can look into the extensive literature of validation studies, and you will come across commonly used terms like ``grid convergence", ``grid sensitivity", ``grid-convergence-index or GCI and so on. You can compare your results with experimental data or direct numerical simulations (if you are solving for turbulent flows say).

Dear Tapan K. Sengupta